BCHM-3050 Lecture Notes - Lecture 5: Exonuclease, Dna Polymerase I, Dna Polymerase Iii Holoenzyme
Chapter 22 – DNA Replication
Information Transfer in the Cell
DNA Replication – template-directed duplication of the DNA genome prior
to cell division. DNA is separated at forks, and replication begins at one or
more fixed sites called replication origins.
It is a semi-conservative model
Bacteria have replication that is uni-directional and the termination and
initiation will occur at the same site. If it is bi-directional, then it occurs at 2
different sites.
Eukaryotic Replication
Eukaryotic replication is bi-directional and has several fixed origins (180
degrees)
They all start at the S PHASE
Prokaryotic vs. Eukaryotic DNA Replication
Similarities
oBi-directional replication
oOrigin sites (# vary)
oReplication Forks
oLeading/Lagging strands
oDNA polymerase synthesizes the new strands 5’ to 3’ direction.
oPrimers are required for a free 3’ OH end
Differences (prokaryotes )
oSimpler packaging of DNA
oCircular Chromosomes, no “ends”
oSMALL genome
oLow # of DNA polymerase copies
Differences (eukaryotes)
oComplex DNA packaging
oLinear Chromosomes
oLARGE genome
oHigh # of DNA polymerase copies
DNA Polymerase
It catalyzes the nucleophilic attack by the 3’ OH at the primer terminus upon
a a-phosphate of the incoming DNTP that is based paired with the template.
It forms a new phosphodiester bond and releases a pyrophosphate
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Document Summary
Dna replication template-directed duplication of the dna genome prior to cell division. Dna is separated at forks, and replication begins at one or more fixed sites called replication origins. Bacteria have replication that is uni-directional and the termination and initiation will occur at the same site. If it is bi-directional, then it occurs at 2 different sites. Eukaryotic replication is bi-directional and has several fixed origins (180 degrees) They all start at the s phase. Similarities: bi-directional replication, origin sites (# vary, replication forks, leading/lagging strands, dna polymerase synthesizes the new strands 5" to 3" direction, primers are required for a free 3" oh end. Differences (prokaryotes : simpler packaging of dna, circular chromosomes, no ends , small genome, low # of dna polymerase copies. Differences (eukaryotes: complex dna packaging, linear chromosomes, large genome, high # of dna polymerase copies.